Piston



FIG. 1 shows our new design of a piston from top in a horizontal view;

FIG. 2 shows the piston straightly from the side;

FIG. 3 shows the piston from below in a horizontal view;

FIG. 4 shows the piston in a first perspective view obliquely from above;

FIG. 5 shows the piston in a first perspective view obliquely from below;

FIG. 6 shows the piston in a second perspective view obliquely form above; and,

FIG. 7 shows the piston in a second perspective view obliquely form below. 

The ornamental design for a piston, as shown and described. 